Jaw structure for electrosurgical instrument

ABSTRACT

An electrosurgical medical device for creating thermal welds in engaged tissue that provides general grasping and dissecting functionality. In an exemplary embodiment, at least one jaw of the instrument defines a tissue engagement plane carrying electrosurgical energy delivery means. The jaw assembly, in one mode of operation, can be used for general grasping and dissecting purposes wherein the jaws close in a non-parallel manner so that the distalmost jaw tip only engage tissue with little movement of the actuator lever in the handle of the instrument. In another mode of operation, the jaw assembly closes close in a parallel manner under very high compression to enable tissue welding.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit from Provisional U.S. Patent ApplicationSer. No. 60/384,429 filed May 31, 2002 having the same title, whichapplication is incorporated herein by this reference. This applicationis a Continuation-In-Part of co-pending U.S. patent application Ser. No.10/032,867 filed Oct. 22, 2001 titled Electrosurgical Jaw Structure forControlled Energy Delivery, and U.S. patent application Ser. No.10/079,728 filed Feb. 19, 2002 titles Electrosurgical Systems andTechniques for Sealing Tissue, both of which are incorporated herein bythis reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to medical devices and techniques and moreparticularly relates to an electrosurgical jaw structure. The jawassembly, in one mode of operation, can be used for general grasping anddissecting purposes wherein the jaws close in a non-parallel manner sothat the distalmost jaw tips only engage tissue with little movement ofthe actuator lever in the handle of the instrument. In another mode ofoperation, the jaw assembly closes in a parallel manner under very highcompression to enable tissue welding.

2. Description of the Related Art

In various open and laparoscopic surgeries, it is necessary tocoagulate, seal or weld tissues. One preferred means of tissue-sealingrelies upon the application of electrical energy to captured tissue tocause thermal effects therein for sealing purposes. Various mono-polarand bi-polar radiofrequency (Rf) jaw structures have been developed forsuch purposes. In a typical bi-polar jaw arrangement, each jaw facecomprises an electrode and Rf current flows across the captured tissuebetween the first and second polarity electrodes in the opposing jaws.While such bi-polar jaws can adequately seal or weld tissue volumes thathave a small cross-section, such bi-polar instruments often areineffective in sealing or welding many types of tissues, such asanatomic structures having walls with irregular or thick fibrouscontent, bundles of disparate anatomic structures, substantially thickanatomic structures, or tissues with thick fascia layers such as largediameter blood vessels.

Prior art Rf jaws that engage opposing sides of a tissue volumetypically cannot cause uniform thermal effects in the tissue, whetherthe captured tissue is thin or substantially thick. As Rf energy densityin tissue increases, the tissue surface becomes desiccated and resistantto additional ohmic heating. Localized tissue desiccation and charringcan occur almost instantly as tissue impedance rises, which then canresult in a non-uniform seal in the tissue. The typical prior art Rfjaws can cause further undesirable effects by propagating Rf densitylaterally from the engaged tissue to cause unwanted collateral thermaldamage.

What is needed is an instrument with a jaw structure that can apply Rfenergy to tissue in new modalities: (i) to weld or seal tissue volumesthat have substantial fascia layers or tissues that are non-uniform inhydration, density and collagenous content; (ii) to weld a targetedtissue region while substantially preventing thermal damage in regionslateral to the targeted tissue; and (iii) to weld a bundle of disparateanatomic structures.

SUMMARY OF THE INVENTION

The principal objective of the present invention is to provide anelectrosurgical jaw structure and Rf energy control system that iscapable of precisely modulating energy to engaged tissue over a selectedtime interval to accomplish tissue welding. As background, thebiological mechanisms underlying tissue fusion or welding by means ofthermal effects are not fully understood. In general, the application ofRf energy to a captured tissue volume causes ohmic heating(alternatively described as active Rf heating herein) of the tissue tothereby at least partially denature proteins in the tissue. By ohmicheating, it is meant that the active Rf current flow within tissuebetween electrodes causes resistive heating of conductive compositions(e.g., water) in the tissue.

One objective of the invention is to denature tissue proteins, includingcollagen, into a proteinaceous amalgam that intermixes and fusestogether as the proteins renature. As the treated region heals overtime, the so-called weld is reabsorbed by the body's wound healingprocess. A more particular objective of the invention is to provide asystem that (i) instantly and automatically modulates ohmic heating oftissue to maintain a selected temperature in the tissue, and (ii) toinstantly and automatically modulate total energy application betweenactive Rf heating (resulting from tissue's resistance to current flowtherethrough) and conductive heating of tissue cause by the thermalcapacity of the jaw components.

In one exemplary embodiment, a jaw of the instrument defines a tissueengagement plane that engages the tissue targeted for welding. Theengagement plane carries first and second surface portions thatcomprise, respectively an electrical conductor and a variable resistivebody or positive temperature coefficient (PTC) material having aresistance that increases at higher temperatures. A variable resistivebody of a dope polymer or ceramic can be engineered to exhibit apositively sloped curve of temperature-resistance over a temperaturerange of about 37° C. to 100° C. The region at the higher end of such atemperature range brackets a targeted “thermal treatment range” at whichtissue can be effectively welded. The selected resistance of thevariable resistive body at the upper end of the temperature range willsubstantially terminate current flow therethrough.

In operation, it can be understood that the engagement plane will applyactive Rf energy (ohmic heating within) to the engaged tissue until thepoint in time that the variable resistive body is heated to exceed themaximum of the thermal treatment range. Thereafter, Rf current flow fromthe engagement surface will be lessened—depending on the relativesurface areas of the first and second surface portions. This instant andautomatic reduction of Rf energy application can be relied on to preventany substantial dehydration of tissue proximate to the engagement plane.By thus maintaining an optimal level of moisture around the engagementplane, the working end can more effectively apply energy to thetissue—and provide a weld thicker tissues with limited collateralthermal effects.

The jaw assembly corresponding to the invention further provides asuitable cross-section and mass for providing a substantial heatcapacity. Thus, when the variable resistive body is elevated intemperature to the selected thermal treatment range, the retained heatof the variable resistive matrix volume can effectively conduct thermalenergy to the engaged tissue volume. Thus, in operation, the working endcan automatically modulate the application of energy to tissue betweenactive Rf heating and passive conductive heating of the targeted tissueto maintain the targeted temperature level.

The jaw assembly corresponding to the invention is moved between an openposition and closed position about an engagement plane by the positiveengagement of the proximally-facing cams and distally-facing camscarried by a reciprocating member. Thus, the jaw assembly can be usedeffectively to dissect tissue by inserting the tip of the jaw assemblyinto a tissue plane and then opening the jaws with substantial from tothus separate and dissect the tissue. This is not possible with many jawassemblies of surgical instrumemts that use springs to move the jawstoward an open position.

Additional objects and advantages of the invention will be apparent fromthe following description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a Type “A” introducer andelectrosurgical jaw assembly illustrating the first and second camsurfaces of the jaws that are adapted for positive engagement with areciprocating member for both closing and opening the jaws.

FIG. 2 is another perspective view of the Type “A” jaw assembly of FIG.1 illustrating the engagement surfaces of the jaws.

FIG. 3 is a perspective view of the reciprocatable extension member ofthe Type “A” electrosurgical working end of FIGS. 1-2 shown de-matedfrom the working end.

FIG. 4 is a plan view of the de-mated reciprocatable member of FIG. 3showing the first and second cam surfaces thereof.

FIG. 5A is an end view of the reciprocatable member of FIG. 3 with firstand second jaws in phantom view.

FIG. 5B is a sectional view of the reciprocatable member of FIG. 3 takenalong line 5A—5A of FIG. 3.

FIG. 6 is a perspective view of a de-mated jaw of the Type “A”electrosurgical working end of FIGS. 1-2.

FIG. 7A is a side view of working end of FIGS. 1 and 2 with thereciprocatable member being retracted to apply opening forces on thepaired jaws.

FIG. 7B is a side view similar to FIG. 7A showing the reciprocatablemember fully extended to apply high compressive forces over the lengthof the paired jaws.

FIG. 8A is a sectional view of the Type “A” electrosurgical jaw takenalong line 8A-8A of FIG. 7B illustrating the conductive componentcarried in one jaw and a variable resistive matrix carried in both jaws.

FIG. 8B is a graph showing the temperature-resistance profile of avariable resistive matrix carried in the jaw of FIG. 8A, the impedanceof tissue and the combined resistance of the variable resistive matrixand tissue as measured by a system controller.

FIG. 8C is a graph showing an alternative temperature-resistance profileof a variable resistive matrix carried in the jaw of FIG. 8A.

FIG. 8D is a sectional view of an alternative Type “A” electrosurgicaljaw illustrating the conductive component and temperature-sensitiveresistive matrix of the jaw assembly carried in a one jaw with the otherjaw having a insulative engagement surface.

FIG. 8E is a sectional view of another alternative Type “A”electrosurgical jaw illustrating the conductive component embedded inthe temperature-sensitive resistive matrix in one jaw.

FIG. 9 is a perspective view of a Type “B” electrosurgical working endwith the jaws in an open position showing first and second cam surfacescarried on a single rotatable jaw.

FIG. 10 is a perspective view of the Type “B” working end of FIG. 9 withthe jaws in a closed position again showing the first and second camsurfaces of the single rotatable jaw.

FIG. 11 is an enlarged view of a proximal (first) end portion of theType “B” jaw of FIGS. 9-10 showing a projecting pin of the upper jawthat rotatably cooperates with an arcuate bore in the lower jaw toprovide a jaw pivot with a selected degree of freedom of movement.

FIG. 12A shows a Type “C” jaw structure in an open position with theslidable extension member and jaws in a partially cut-away view toillustrate the jaw opening-closing mechanism.

FIG. 12B shows the Type “C” jaw structure of FIG. 12A in a first closedposition with the slidable extension member moving the jaws to aparallel condition.

FIG. 12C shows the jaw structure of FIGS. 12A-12B in a second closedposition with the slidable extension member moving the jaws to anon-parallel condition so that the distalmost jaw tips engage tissue.

FIG. 12D shows the jaw structure of FIGS. 12A-12C in a third closedposition with the slidable extension member moving the jaws to ahigh-compression parallel condition for tissue welding.

FIG. 13 shows the slidable extension member of FIGS. 12A-12D de-matedfrom the first and second jaws to show the first and second camelements.

DETAILED DESCRIPTION OF THE INVENTION

1. Type “A” jaw assembly. An exemplary Type “A” jaw assembly 100 of asurgical grasping instrument is illustrated in FIGS. 1 and 2 which isadapted for transecting captured tissue and contemporaneous welding ofthe captured tissue with Rf energy delivery. The jaw assembly 100 iscarried at the distal end 104 of an introducer sleeve member 106 thatcan be rigid, articulatable or deflectable in any suitable diameter. Forexample, the introducer sleeve portion 106 can have a diameter rangingfrom about 2 mm., to 20 mm. to cooperate with cannulae in endoscopicsurgeries or for use in open surgical procedures. The introducer portion106 extends from a proximal handle (not shown). The handle can be anytype of pistol-grip or other type of handle known in the art thatcarries actuator levers, triggers or sliders for actuating the jaws aswill be disclosed below, and need not be described in further detail.The introducer sleeve portion 106 has a bore 108 extending therethroughfor carrying actuator mechanisms for actuating the jaws and for carryingelectrical leads 109 a-109 b for the electrosurgical components of theworking end.

As can be seen in FIGS. 1 and 2, the jaw assembly 100 has first (lower)jaw element 112A and second (upper) jaw element 112B that are adapted toclose or approximate about axis 115. The jaw elements may both bemoveable or a single jaw may rotate to provide the open and closedpositions. In the exemplary embodiment of FIGS. 1 and 2, both the lowerand upper jaws 112A-112B are moveable relative to a rolling pivotlocation 116 defined further below. Another exemplary embodiment with afixed lower jaw portion 112A and rotatable upper jaw 112B is shown inFIGS. 9 and 10.

Of particular interest, the opening-closing mechanism of the jawassembly 100 corresponding to the invention operates on the basis of cammechanisms that provide a positive engagement of camming surfaces (i)for moving the jaw assembly to the (second) closed position to engagetissue under very high compressive forces, and (ii) for moving the jawstoward the (first) open position to apply substantially high openingforces for “dissecting” tissue. This important feature allows thesurgeon to insert the tip of the closed jaws into a dissectable tissueplane—and thereafter open the jaws to apply such dissecting forcesagainst the tissues (see FIG. 7A).

Referring to FIGS. 1 and 2, the lower and upper jaws 112A-112B have afirst end 118, in the open position, that defines first(proximally-facing) arcuate outer surface portions indicated at 120 aand 120 b that are engaged by a first surface portions 122 a and 122 bof reciprocatable member 140 that is adapted to slide over the jawelements to thereby move the jaws toward closed position. The first endportion 118 of the lower and upper jaws, in the open position, furtherdefines second (distally-facing) arcuate surface portions indicated at130 a and 130 b that are engaged by second surface portions 132 a and132 b of the reciprocatable member 140 for moving the jaw elements tothe open position. The distal (second) end region 133 of the paired jawsis rounded with a lip 134 that can serve as an electrode for surfacecoagulation as will be described below.

In this embodiment of FIGS. 1 and 2, the reciprocating member 140 (seeFIGS. 3 and 4) is actuatable from the handle of the instrument by anysuitable mechanism, such as a lever arm, as is known in the art that iscoupled to a proximal end 141 of member 140. The proximal end 141 andmedial portion 141′ of member 140 are dimensioned to reciprocate withinbore 108 of introducer sleeve 106. The distal portion 142 ofreciprocating member 140 carries first (lower) and second (upper)laterally-extending flanges or shoulder elements 144A and 144B that arecoupled by intermediate transverse element 145. The transverse element145 further is adapted to transect tissue captured between the jaws witha leading edge 146 (FIG. 3) that can be a blade or a cutting electrode.The transverse element 145 is adapted to slide within a channels 148 aand 148 b in the paired first and second jaws. As can be seen best inFIGS. 3 and 4, the laterally-extending shoulder elements 144A and 144Bdefine the surfaces 122 a, 122 b, 132 a and 132 b that slidably engagethe arcuate cam surfaces of the jaws and that apply high compressiveforces to the jaws in the closed position (FIG. 7B).

Referring back to FIGS. 1 and 2, the first and second jaws 112A and 112Bdefine tissue-engaging surfaces or planes 150 a and 150 b that contactand deliver energy to engaged tissues, in part, from an Rf electrodearrangement therein indicated at 155. The jaws can have any suitablelength with teeth or serrations 156 in any location for gripping tissue.The embodiment of FIGS. 1 and 2 depicts such serrations 156 at an innerportion of the jaws along channels 148 a and 148 b thus leavingengagement planes 150 a and 150 b laterally outward of thetissue-gripping elements. In the embodiments described below, theengagement planes 150 a and 150 b and electrode(s) 155 generally areshown with a non-serrated surface for clarity of explanation, but suchengagement planes and electrodes themselves can be any non-smoothgripping surface. The axial length of jaws 112A and 112B indicated at Lcan be any suitable length depending on the anatomic structure targetedfor transection and sealing and typically will range from about 10 mm.to 50 mm. The jaw assembly can apply very high compression over muchlonger lengths, for example up to about 200 mm. for example resectingand sealing organs such as a lung or liver. The scope of the inventionalso covers jaw assemblies for an instrument used in micro-surgerieswherein the jaw length can be as little as about 5.0 mm.

In the exemplary embodiment of FIGS. 1 and 2, the engagement plane 150 aof the lower jaw 112A is adapted to deliver energy to tissue, and thetissue-contacting surface 150 b of upper jaw 112B can beelectrosurgically active or passive as will be described below.Alternatively, the engagement surfaces of the jaws can carry any of theelectrode arrangements disclosed in co-pending U.S. patent applicationSer. No. 09/032,867 filed Oct. 22, 2001 titled Electrosurgical JawStructure for Controlled Energy Delivery and Ser. No. 10/308,362 filedDec. 3, 2002 titled Electrosurgical Jaw Structure for Controlled EnergyDelivery both of which are incorporated herein by reference.

The perspective and plan views (FIGS. 3 and 4) more particularlyillustrate the cam surfaces of reciprocating member 140 de-mated fromjaws 112A and 112B. FIG. 5A shows an end view of “I”-beam shape of thereciprocating member 140 with the jaws 112A and 112B in phantom view.From FIGS. 3, 4 and 7B, it can be easily understood how the jaw assembly100 can apply very high compressive pressures to engaged tissue. Thetransverse element 145 of the reciprocating member 140 defines atransverse dimension d between the innermost surfaces 158 a and 158 b ofthe flanges of the reciprocating member and the cooperating medial anddistal outer surfaces 160A and 160B of the jaws (see FIGS. 6, 7A and7B). The selected transverse dimension d between the flanges orshoulders 144A and 144B thus further defines the engagement gap gbetween the engagement planes 150 a and 150 b of the jaws in the closedposition. It has been found that very high compression of tissuecombined with controlled Rf energy delivery is optimal for welding theengaged tissue volume contemporaneous with transection of the tissue.Preferably, the engagement gap g between the engagement planes rangesfrom about 0.001″ to about 0.050″ for most tissue volumes. Morepreferably, the gap g between the engagement planes ranges from about0.001″ to about 0.010″. As can be seen in FIGS. 3, and 5B, the medialportion 141″ of the reciprocating member 140 retains an “I”-beam shapewith inner surface portions 163 a and 163 b that engage the cooperatingmedial outer surfaces of the jaws. Thus, the entire length L of the jawscan be maintained in a fixed spaced-apart relationship to define aconsistent engagement gap g—no matter the length of the jaws.

It should be appreciated that jaw assembly 100 can be provided withmechanisms for adjusting the transverse dimension d between the innersurfaces of flanges 144A and 144B of the reciprocating member 140 as aredisclosed in co-pending U.S. patent application Ser. No. 09/017,452filed Dec. 13, 2001 titled Electrosurgical Jaws for ControlledApplication of Clamping Pressure which is incorporated herein byreference. That application discloses mechanisms that allow the operator(i) to adjust the transverse dimension d between the cam surfaces ofshoulders 144A and 144B between pre-selected dimensions, or (ii) toallow for dynamic adjustment of the transverse dimension d in responseto the tissue volume captured between the paired jaws.

FIG. 6 shows an exemplary jaw de-mated from the jaw assembly 100 thatexposes the cam engagement surfaces 120 b and 130 b of the member. Anadditional unique feature of the invention is the fact that thecooperating jaws can be identical to one another, thus simplifying themanufacturing process. Since the jaw members can be identical, metalinjection molds costs can be reduced.

FIGS. 7A and 7B more particularly show the actuation of thereciprocating member 140 from a first retracted position to a secondextended position to move the jaws 112A and 112A from the first openposition to the second closed position. Referring to FIG. 7A, it can beseen that the translatable member 140 is being moved in the proximaldirection so that the proximal-facing surfaces 132 a and 132 b ofreciprocating member 140 abut the outer surfaces 130 a and 130 b of thejaws thus forcing the jaws apart, for example to apply dissecting forcesto tissues. FIG. 7B shows the reciprocating member 140 after having beenfully extended in the distal direction so that the distal-facingsurfaces 122 a and 122 b of reciprocating member 140 have ridden up andover the proximal arcuate surfaces 120 a and 120 b of the jaws (andmedial outer surfaces 160A′ and 160B′) thus forcing the jaws together.

Of particular interest, the jaws can rollably contact one another alongthe interface 170 between inner surfaces 172 a-172 b of the first end118 of the jaws (see FIGS. 6, 7A and 7B). Thus, the jaw assembly doesnot need to define a true single pivot point as is typical of hinge-typejaws known in the art. The pivotable action of the jaws along interface170 can best be described as a rolling pivot that optionally can allowfor a degree of dynamic adjustment of the engagement gap g′ at theproximal end of the jaws. The jaws elements can be retained relative toone another and the introducer sleeve 106 by means of protrudingelements 175 (FIG. 6) that couple with arcuate slots 176 in an internalmember 177 that is fixedly carried in bore 108 of introducer sleeve 106.Alternatively, outwardly protruding elements 178 can cooperate withslots in the wall of introducer sleeve 106 (not shown). As also shown inFIG. 6, the jaw assembly can (optionally) include springs for urging thejaws toward the open position. Electrical leads indicated at 109 a-109 bare shown in FIG. 6 for coupling a voltage source (radiofrequencygenerator) 180 and controller 182 to the electrode arrangement 155.

In one preferred embodiment shown in FIGS. 1 and 2, the first (lower)jaw 112A carries an exposed conductive material or electrode 155together with an exposed variably resistive matrix 185 in the jaw'sengagement plane 150 a. The jaw assembly carries a return electrode inany of three locations, or any combination thereof: (i) in a portion ofthe opposing engagement surface 150 b of upper jaw 112B, (ii) in thetransverse element 145 of the reciprocating member 140; or (iii) inlaterally outward portions of the lower jaw 112A that surround thevariably resistive matrix 185.

The sectional view of FIG. 8A more particularly illustrates the relevantconductive and variably resistive components within the body of thelower jaw 112A for controllably delivering energy to tissue for sealingor welding purposes. The engagement surface 150 a of jaw 112A has theexposed conductive material (electrode) indicated at 155 that is bothelectrically conductive and thermally conductive. For example, theconductive material 155 can comprise a machined metal, a formed metal ora molded metal having a substantial thickness—that can be conductivelybonded to the positive temperature coefficient (PTC) variably resistivematrix 185 described next. Alternatively, the conductive material 155can comprise a thin film deposit of any suitable material known in theart (e.g., gold, platinum, palladium, silver, stainless steel, etc.)having any suitable thickness dimension, for example, ranging from aboutof 0.0001″ to 0.020″. The width of the conductive material 155 can beany suitable dimension depending on the jaw dimension.

As can be seen in FIG. 8A, the jaw 112A has an engagement surface withan exposed conductive material 155 at least partially surrounded by PTCmatrix 185 that is variably resistive in response to temperature changestherein is carried adjacent to, and inward of, the surface conductivematerial 155. The structural body portion 186 a of jaw 112A can be anysuitable metal or other material having sufficient strength to applyhigh compressive forces to the engaged tissue, and typically carries aninsulative coating (at least on its outer portions). As shown in FIG.8A, the body portion 186 a of jaw 112A preferably (but optionally) has athin insulated coating 187 about its surface to prevent electricalenergy delivery to tissues about the exterior of the jaw assembly andbetween the body 186 a and the PTC matrix 185.

The conductive portion (electrode) 155 exposed in the engagement plane150 a is coupled by an electrical lead 109 a to a voltage (Rf) source180 and controller 182. The matrix 185 can have any suitablecross-sectional dimensions, indicated generally at sd₁ and sd₂, andpreferably such a cross-section comprises a significant fractionalvolume of the jaw body to provide a thermal mass for optimizing passiveconduction of heat to tissue as will be described below.

It can be seen in FIG. 8A, a substantial portion of the surface area ofengagement plane 150 a comprises the PTC resistive matrix 185.Preferably, the matrix 185 comprises at least 10% of the surface area ofengagement plane 150 a of an electrosurgical jaw, wherein the engagementplane is defined as the tissue-contacting surface of the jaw. Morepreferably, the PTC matrix 185 comprises at least 25% of the surfacearea of engagement plane 150 a of such a jaw. Still more preferably, thePTC matrix 185 comprises at least 50% of the surface area of the jaw'sengagement plane 150 a.

Of particular interest, still referring to FIG. 8A, the variablyconductive matrix 185 comprises a polymeric material having atemperature-dependent resistance. Such materials are sometimes known aspolymer-based “temperature coefficient” materials that exhibit verylarge changes in resistance with a small change in body temperature.This change of resistance with a change in temperature can result in a“positive” coefficient of resistance wherein the resistance increaseswith an increase in temperature (a PTC or positive temperaturecoefficient material). The scope of the invention also includes avariably conductive matrix 185 with a “negative” coefficient ofresistance (and NTC material) wherein its resistance decreases with anincrease in temperature.

In one preferred embodiment, the PTC matrix 185 is a ceramic layer thatis engineered to exhibit unique resistance vs. temperaturecharacteristics that is represented by a positively slopetemperature-resistance curve in FIG. 8A. More in particular, the matrix185 maintains a low base resistance over a selected temperature rangewith a dramatically increasing resistance above a selected narrowtemperature range of the material (sometimes referred to herein asswitching range; see FIG. 8B). For example, the base resistance can below, or electrical conductivity can be high, between about 37° C. and65° C., with the resistance increasing greatly between about 55° C. and80° C. In another embodiment, the PTC matrix 185 is characterized by amore continuously positively sloped temperature-resistance as showncurve in FIG. 8C over the range of 37° C. to about 80° C.

One aspect of the invention relates to the use of a PTC matrix 185 asdescribed in FIG. 8B in a jaw's engagement plane with a selectedswitching range between a first temperature (T₁) and a secondtemperature (T₂) that approximates the targeted tissue temperature for acontemplated tissue sealing or welding objective. The selected switchingrange, for example, can be any substantially narrow 1°-10° C. range thatis determined to be optimal for tissue sealing or welding (e.g., any 5°C. range between about 50°-200° C.) or for another thermotherpy. A morepreferred switching range can fall within the larger range of about50°-90° C.

No matter the character of the slope of the temperature-resistance curveof the PTC matrix 185 (see FIGS. 8B and 8C), a preferred embodiment hasa matrix 185 that is engineered to have a selected resistance to currentflow across its selected dimensions in the jaw assembly when at 37° C.ranging from about 0.0001 ohms to 1000 ohms. More preferably, the matrix185 has a designed resistance across its selected dimensions in the jawwhen at 37° C. ranging from about 1.0 ohm to 1000 ohms. Still morepreferably, the matrix 185 has with a designed resistance across itsselected dimensions when at 37° C. ranging from about 25 ohms to 150ohms. In any event, the selected resistance across the matrix 185 in anexemplary jaw at 37° C. exceeds the resistance of the tissue or bodystructure targeted for treatment. The matrix 185 further is engineeredto have a selected resistance that substantially prevents current flowtherethrough corresponding to a selected temperature that constitutesthe high end (maximum) of the targeted thermal treatment range. Such amaximum temperature for tissue welding can be a selected temperaturebetween about 50° C. and 100° C. More preferably, the selectedtemperature at which the matrix's selected resistance substantiallyprevents current flow occurs at between about 60° C. and 90° C.

In a first mode of operation, it can be understood that the initialdelivery of Rf energy to conductor or electrode 155 will thereby applyRf energy to (or cause active ohmic heating of) tissue engaged betweenjaws 112A and 112B. Further, the delivery of Rf energy to electrode 155will be conducted, in part, through the PTC matrix 185 in a path to areturn electrode—no matter the location of the return electrode (or andcombination thereof) as described above. The engaged tissue is thuselevated in temperature by ohmic or “active” Rf heating. The pairedjaws' components, including the PTC matrix 185, will increase intemperature as caused by conduction of heat from the transient hightemperatures of tissue—which were heated by caused by Rf densitiestherein (ohmic heating).

At a selected temperature at the maximum of the targeted treatmentrange, the PTC matrix 185 will no longer contribute to ohmic tissueheating due to termination of current flow therethrough. However, themass of the PTC matrix 185 will still conduct heat to engaged tissue. Asthe PTC matrix 185 falls below the targeted treatment range, the matrix185 again will contribute to ohmic tissue heating via current pathstherethrough from electrode 155. By this means of energy delivery, themass of the jaw body will be modulated in temperature, similar to theengaged tissue, at or about the targeted treatment range. Of particularinterest, the jaw body will apply energy to engaged tissue by ohmicheating, or by conduction (or radiation) of thermal effects in aself-modulating manner.

A suitable PTC material can be fabricated from high puritysemi-conducting ceramics, for example, based on titanate chemicalcompositions (e.g., BaTiO₃, SrTiO₃, etc.). The specificresistance-temperature characteristics of the material can be designedby the addition of dopants and/or unique materials processing, such ashigh pressure forming techniques and precision sintering. Suitable PTCmaterials are manufactured by several sources and can be obtained, forexample, from Western Electronic Components Corp., 1250-A Avenida Acaso,Camarillo, Calif. 93012. Another manner of fabricating the PTC resistivematrix 185 is to use a commercially available epoxy that is doped with atype of carbon. In fabricating a PTC matrix 185 in this manner, it ispreferable to use a carbon type that has single molecular bonds. It isless preferable to use a carbon type with double bonds which has thepotential of breaking down when used in thin layers, thus creating thepotential of an electrical short circuit between the conductor(electrode) 155 and a return electrode carried within the jaw assembly.

As can be seen in FIG. 8A, the conductive material or electrode 155 isoperatively connected to the voltage (Rf) source 180 by electrical lead109 a that defines a first polarity. As described previously, returnelectrode functionality can be carried in any of three components of thejaw assembly, or any combination thereof: (i) in a portion of theopposing engagement surface 150 b of upper jaw 112B, (ii) in thetransverse element 145 of the reciprocating member 140; or (iii) inlaterally outward portions of the lower jaw 112A outwardly adjacent tothe PTC matrix 185. In the embodiment of FIG. 8A, the body portions 186a and 186 b of the lower and upper jaws 112A and 112B have an opposingpolarity as defined by coupling to electrical source by lead 109 b.Further, the slidable contact of the jaw body portions 186 a and 186 bwith transverse element 145 of reciprocating member 140 makes itfunction with the opposing polarity. In the preferred embodimentdepicted in FIG. 8A, the upper jaw 112B also carries a PTC matrix 185that covers a substantial portion of the engagement surface 150 b. Thematerial of the PTC matrix can be identical in both the lower and upperjaws.

The manner of utilizing the jaw assembly 100 of FIG. 8A to perform amethod of the invention can be understood as engaging and compressingtissue between the first and second engagement surfaces 150 a and 150 bof jaws 112A and 112B and thereafter delivering Rf energy from conductor155 and PTC matrix 185 to maintain a selected temperature in the engagedtissue for a selected time interval. For example, the jaw assembly isprovided with a PTC matrix 185 that has a targeted treatment range in aregion below about 90° C. With the jaws in the closed position and theengagement planes 150 a and 150 b engaging tissue, the operator actuatesa switch that delivers Rf energy from the voltage (Rf) source 180 to theconductor 155. At normal tissue temperature, the low base resistance ofthe PTC matrix 185 allows unimpeded Rf current flow from the voltagesource 180 through engagement surface 150 a and tissue to the returnelectrode components as described above via lead 109 b. It can beunderstood that the engaged tissue initially will have a substantiallyuniform impedance to electrical current flow, which will increasesubstantially in proximity to engagement surfaces 150 a and 150 b as theengaged tissue loses moisture due to ohmic heating.

Following an arbitrary time interval, the impedance of tissue proximateto engagement surfaces 150 a and 150 b will be elevated, and the highertissue temperature will instantly conduct heat to the PTC matrix 185 ineach jaw. In turn, the PTC matrix 185 will reach its limit and terminateRf current flow therethrough. Such automatic reduction of active Rfenergy application can thus prevent any substantial dehydration oftissue proximate to PTC matrix 185. By thus maintaining the desiredlevel of moisture in tissue proximate to the engagement planes, the jawassembly can more effectively apply energy to the tissue. Such energyapplication can extend through thick engaged tissue volumes whilecausing very limited collateral thermal effects. Thereafter, as thetemperature of the engaged tissues falls by thermal relaxation and thelesser Rf energy density, the temperature of the matrix 185 will fallbelow the threshold of the targeted treatment range. This effect, inturn, will cause increased Rf current flow through the assembly andmatrix to the engaged tissues to again increase the tissue temperatureby increased ohmic heating. By the above-described mechanisms of causingthe PTC matrix 185 to be maintained in the treatment range, the actualRf energy applied to the engaged tissue can be precisely modulated tomaintain the desired temperature in the tissue. Further, the compositionthat comprises matrix 185 can comprise a substantial volume of the jaws'bodies and the thermal mass of the jaws, when elevated in temperature,can deliver energy to the engaged tissue by means of passive conductiveheating—at the same time Rf energy delivery causes lesser active (ohmic)tissue heating. This balance of active Rf heating and passive conductive(or radiative) heating can maintain the targeted temperature for anyselected time interval.

In summary, one method of the invention comprises the delivery of Rfenergy from a voltage source 180 to tissue via a conductor in a jawassembly at least partly through a PTC material 185 wherein thethermally-sensitive resistor material has a selectedtemperature-resistance profile to provides low resistance at low tissuetemperatures and a very high resistance above the targeted temperaturerange for tissue sealing or welding. In operation, the working endautomatically modulates active Rf energy density in the tissue as thetemperature of the engaged tissue conducts heat back to the PTC material185 to cause move the matrix along its selected temperature-resistancecurve. In the treatment range, the Rf current flow thus can be modulatedwithout the need for thermocouples or any other form of feedbackcircuitry mechanisms to modulate Rf power from the source. Mostimportant, it is believed that this method of the invention will allowfor immediate modulation of actual Rf energy application along theentire length of the jaws, which is to be contrasted with prior artinstruments that utilize a temperature sensor and feedback circuitry.Such sensors or thermocouples measure temperature only at a singlelocation in the jaws, which typically will not be optimal for energydelivery over the length of the jaws. Such temperature sensors alsosuffer from a time lag. Further, such temperature sensors provide onlyan indirect reading of actual tissue temperature—since a typical sensorcan only measure the temperature of the electrode.

In another mode of operation, the system controller 182 coupled tosource 180 can acquire data from the current flow circuitry that iscoupled to first and second polarity electrodes in the jaw (in anylocations described previously) to measure the blended impedance ofcurrent flow between the first and second polarity conductors throughthe combination of (i) the engaged tissue and (ii) the PTC matrix.Another method of the invention thus can include provide algorithmswithin the system controller 182 to modulate, or terminate, powerdelivery to working end based on the level of the blended impedance asdefined above. The method can further include controlling energydelivery by means of power-on and power-off intervals, with each suchinterval having a selected duration ranging from about 1 microsecond toone second. The working end and system controller 182 can further beprovided with circuitry and working end components of the type disclosedin Provisional U.S. Patent Application Ser. No. 60/339,501 filed Nov. 9,2001 titled Electrosurgical Instrument which is incorporated herein byreference.

In another mode of operation, the system controller 182 can be providedwith algorithms to derive the temperature of the resistive PTC matrix185 from measure impedance levels—which is possible since the matrix isengineered to have a selected resistance at each selected temperatureover the temperature-resistance curve (see FIGS. 8B-8C. Such temperaturemeasurements can be utilized by the system controller 182 to modulate,or terminate, power delivery to engagement surfaces based on thetemperature of the PTC matrix 185. This method also can control energydelivery by means of the power-on and power-off intervals as describedabove.

Referring back to FIG. 2, the distal (second) end 133 of the jawscarries a thin lip 134 extending outwardly from the jaw body. It hasbeen found useful to provide an electrode in lip 134 for surfacecoagulation of tissues. In one preferred embodiment, an independentelectrode 188 is carried in lip 134 that can be any thin film conductivematerial carried at the surface of jaws and coupled to an electricalsource (not shown), for example cooperating with a ground pad. Inanother embodiment, the electrode 188 can comprise an exposed portion ofthe conductive lower jaw body 186 a and upper jaw body 186 b wherein theinsulative layer 187 removed from the lips 134 (cf. FIG. 8A).

FIG. 8D shows an alternative embodiment of jaw assembly 190 that carriesall the same components as described previously in the embodiment ofFIG. 8A. The difference is that the engagement plane 150 b of upper jaw112B carries a fully insulated layer indicated at 192. It has been foundthat such a configuration can function well in very small instrumentsadapted for engaging small tissue volumes.

FIG. 8E illustrates another alternative embodiment of jaw assembly 195that carries components that are similar to those described in theembodiments of FIGS. 8A and 8D. However, in this embodiment, theconductor 155 of the lower jaw 112A is carried in an interior portion ofthe PTC matrix 185. Thus, the conductor 155 has no exposed surface inengagement plane 150 a of the lower jaw 112A. It has been found thatsuch a configuration is useful in treating some very thin tissues sinceohmic heating of tissue can be terminated altogether when the PTC matrix185 reaches its selected switching range. In operation, the jaws canautomatically modulate the application of energy to tissue betweenactive Rf heating and passive conductive heating of the targeted tissueat a targeted temperature level.

2. Type “B” jaw assembly. FIGS. 9-10 illustrate an exemplary Type “B”jaw assembly 200 adapted for electrosurgery that again can weld andtransect an engaged tissue volume. The jaw assembly 200 is carried atthe distal end 204 of an introducer member 206 that has a bore 208extending therethrough. The Type “B” embodiment is similar to the Type“A” embodiment except that the first (lower) jaw 212A is a fixedextension portion of rigid introducer member 206. As can be seen inFIGS. 9 and 10, the second (upper) jaw 212B is adapted to close orapproximate about axis 215.

The opening-closing mechanism of jaw assembly 200 corresponding to theinvention again provides cam surfaces for positive engagement betweenreciprocatable member 240 and the jaws (i) for moving the jaws to a(second) closed position to engage tissue under high compressive forces,and (ii) for moving the jaws toward the (first) open position therebyproviding high opening forces to dissect tissue with outer surfaces ofthe jaw tips. The reciprocating member 240 operates as describedpreviously to reciprocate within bore 208 of the introducer member 206.As can be seen in FIG. 10, the distal end portion 242 of reciprocatingmember 240 carries distal first and second laterally-extending flangeportions 244A and 244B with the blade-carrying transverse element 245extending therebetween. The blade-carrying member slides within channels248 a and 248 b in the jaws.

In the exemplary embodiment of FIGS. 9 and 10, the first and second jaws112A and 112B again define engagement surfaces or planes 250 a and 250 bthat deliver energy to engaged tissue. The engagement planes carry aconductor 255 and a PTC matrix 285 in at least one of the jaws'engagement surfaces 250 a and 250 b. In the embodiment of FIGS. 9 and10, the upper jaw 212B has a first end region 258 that, in the openposition, defines a first (proximally-facing) arcuate cam surfaceindicated at 260 that is engaged by a first surface portion 262 of thereciprocatable member 240. The reciprocatable member 240 can besubstantially identical to that of FIGS. 3 and 4. The first (proximal)end region 258 of the upper jaw, in the open position, further definessecond (distally-facing) surface portions indicated at 270 a and 270 a′that are engaged by second surface 272 of reciprocatable member 240 formoving the jaw assembly to an open position.

As can be seen best in FIG. 10, the cam surfaces 270 a and 270 a′ areformed into pins or projecting elements 274 and 274′ that serve multiplepurposes. Referring to FIG. 11, the pins 274 and 274′ extend through theupper jaw body 276 b and are received within arcuate bores 277 in body276 a of lower jaw 212A. The lower portions 278 (collectively) of thepins 274 and 274′ thus can retain upper jaw 212A and prevent it frommoving axially or laterally relative to the jaw axis 215 while stillallowing the jaw's rotation for opening and closing. The pin mechanismfurther allows for greatly simplified assembly of the instrument.

Of particular interest, the pins 274 and 274′ provide additionalfunctionality by providing a degree of “vertical” freedom of movementwithin the first (proximal) end portion 258 of the jaw. As can be seenin FIGS. 10 and 11, the distal laterally-extending flange portions 244Aand 244B define a transverse dimension d (cf. FIG. 3) that in turndetermines the dimension of the engagement gap g of the distal end ofthe jaws in the jaw-closed position (FIG. 10). The transverse dimensiond equals the dimension between inner surfaces of flange portions 244Aand 244B that slidably contact the outer surfaces of both jaws.

FIG. 10 further illustrates that reciprocatable member 240 carriesseparate proximal laterally-extending flange portions 294A and 294B withan optional different transverse dimension d′ between inner surfacesthereof. A larger dimension d′ between flange portions 294A and 294Bthat slidably contacts the proximal surfaces of both jaws can thusprovide a different engagement gap g′ at the proximal end of the jaws.This selected gap dimension g′ can be larger than the engagement gap gat the distal end of the jaws—an effect that would not be possible witha hinged jaw that allows no “vertical” freedom of movement between theproximal ends of the jaws. It has been found that such a floating pivotis useful for engaging thick tissues. Further, the inner surfaces of theflanges 244A-244B and 294A-294B can carry a very slightly compressiblematerial such as a Teflon (not shown) wherein slight compression of suchmaterial would allow the jaws' engagement surfaces to move slightlyapart when engaging thick tissues.

3. Type “C” jaw assembly. FIGS. 12A-12D illustrate an exemplary Type “C”jaw assembly 300 that provides both electrosurgical functionality andimproved grasping and dissecting functionality for endoscopic surgeries.In FIGS. 12A-12D, both the upper and lower jaws are shown in cut-awayviews to show internal cam surfaces of the upper jaw 312A and thereciprocatable member 240. The jaw assembly 300 carries engagementsurfaces for applying electrosurgical energy to tissue as in thepreviously described embodiments, as well as cutting means fortransecting the engaged tissue volume. The improvement of the Type “C”jaw assembly 300 relates to the ability of the jaw structure, in onemode of operation, to be used for general grasping and dissectingpurposes wherein the distalmost tips 313 of the jaws can close tightlyon tissue with little movement of the actuator lever in the handle ofthe instrument. At the same time, in another mode of operation, the jawassembly 300 can close to apply very high compressive forces on thetissue to enable welding. Thus, the jaw structure provides (i) a firstnon-parallel jaw-closed position for grasping tissue with the distaljaws tips (FIG. 12C), and (ii) a second parallel jaw-closed position forhigh compression of tissue for the application of electrosurgical energy(FIG. 12D).

Referring to FIG. 12A, the Type “C” embodiment again has an introducermember 206 that is similar to the Type “B” embodiment with first (lower)jaw 312A comprising a fixed extending portion 314 of the rigidintroducer. As can be seen in FIG. 12A, the second (upper) jaw 312B isadapted to close or approximate about axis 315. The opening-closingmechanism of jaw assembly 300 provides cam elements and cooperating jawsurfaces for positive engagement between the reciprocatable member 240as described previously (i) for moving the jaws to a closed position toengage tissue, and (ii) for moving the jaws toward the open positionthereby providing high opening forces to dissect tissue with outersurfaces of the jaw tips 313.

The reciprocating member 240 (FIG. 13) operates as described previouslyto reciprocate within bore 208 of the introducer member 206 (FIG. 12A).As can be seen in FIG. 12A, the distal end 242 of the reciprocatingmember 240 again carries distal flange portions 244A and 244B with ablade-carrying transverse portion 245 therebetween. The transverseportion 245 slides within channels 248 a and 248 b in the paired jaws.In the exemplary embodiment of FIG. 12A, the first and second jaws 312Aand 312B again define engagement surfaces 350 a and 350 b that candeliver electrosurgical energy to engaged tissue. The engagement planespreferably carry a conductive-resistive matrix 385 (not shown) in atleast one of the jaws' engagement surfaces.

In the embodiment of FIG. 12A, the upper jaw 312B has a proximal end 258that defines a first (proximally-facing) arcuate jaw surface 260 that isengaged by a first cam surface element 262 of reciprocatable member 240for opening the jaw. The proximal end 258 of the upper jaw furtherdefines second (distally-facing) jaw surface portions indicated at 270 aand 270 a′ that are engaged by second cam element 272 of reciprocatablemember 240 for moving the jaw assembly to an open position.

The embodiment of FIG. 12A shows that the upper jaw 312B has a floatingprimary pivot location indicated at P₁ that is provided by theprojecting elements or rectangular pins 274 (collectively) on eitherside of the channel portions 248 a that slidably extend into bores 277(collectively) in the lower jaw body (cf. FIG. 11). The lower portionsof the pins 274 thus allow upper jaw 312B to rotate while at the sametime the pin-and-bore mechanism allows the upper jaw to move upwardlyaway from the lower jaw.

Of particular interest, the degree of “vertical” freedom of movement ofthe upper jaw allows for the system to “tilt” the distal tip 313 ofupper jaw 312B toward the axis 315 to thereby allow the distal jaw tips313 to grasp tissue. This is termed a non-parallel closed positionherein. The tilting of the jaw is accomplished by providing a pluralityof cam surfaces in the upper jaw 312B and the reciprocatable member 240.

As can be seen in FIGS. 12A and 13, the lower and upperlaterally-extending flange portions 244A and 244B of the reciprocatablemember 240 define a transverse dimension d that determines the dimensionof gap g between the engagement surface of the jaws in the fullyjaw-closed position (FIGS. 10 & 12D). The transverse dimension d equalsthe dimension between inner surfaces of flange portions 244A and 244Bthat slidably contact the outer surfaces of both jaws.

FIG. 13 best illustrates that the reciprocatable member 240 isconfigured with separate elevated step or cam surfaces 390 in the lowerflange portions 244A that are adapted to slidably engage the ends 395 ofthe rectangular pins 274 on either side of upper jaw 312B. The elevatedcam surfaces 390 of reciprocatable member 240 thus create anothertransverse dimension d′ between inner surfaces of the flange portions244A and 244B that move the jaws toward either the first jaw-closedposition or the second jaw-closed position.

Now turning to FIGS. 12A-12D, the sequence of cut-away views illustratehow the multiple cam surfaces cause the jaws to move between a first“tilted” jaw-closed position to a second “high-compression” jaw-closedposition. In FIG. 12A, the jaws are in an open position. In FIG. 12B,the reciprocatable extension member 240 is moved distally and its camsurface element 262 pushes on jaw surfaces 260 to move the jaws toward aclosed position wherein the jaws rotate about primary pivot location P₁.In FIG. 12B, it can be seen that the elevated cam surfaces 390 in thelower flange 244A have not yet engaged the ends 295 of the rectangularpins 274.

Now turning to FIG. 12C, the extension member 240 is moved furtherdistally wherein the elevated cam surfaces 390 of lower flange 244A havenow engaged and elevated the ends 295 of rectangular pins 274 therebytilting the upper jaw. The upper jaw 312B is tilted slightly by forcesin the direction of the arrows in FIG. 12C as the upper flange 244Bholds the upper jaw 312B at a secondary pivoting location indicated atP₂—at the same time that the step of the cam surface element 390 liftsthe pins 274 and the proximal portion 258 of the upper jaw 312B upward.

Thus, the system functions by providing a slidable cam mechanism forlifting the proximal end of the jaw while maintaining the medial jawportion in a fixed position to thereby tilt the distal jaw to the secondjaw-closed position, with the pivot occurring generally about secondarypivot P₂ which is distal from the primary pivot location P₁.

FIG. 12D next shows the reciprocatable extension member 240 movedfurther distally wherein the elevated cam surfaces 390 of lower flange244A slides distally beyond the ends 295 of rectangular pins 274 thuscausing the flanges 244A and 244B together with the trailing edgeportions 354A and 354B of the “I”-beam portion (FIG. 13) of the member240 to apply very high compression forces over the entire length of thejaws as indicated by the arrows in FIG. 12D. This position is termed aparallel jaw-closed position herein. Another advantage of the inventionis that the jaw structure is in a “locked” position when the extensionmember 240 is fully advanced. The instrument does not need a separatemechanism to maintain the jaws locked together as in prior art graspers.

FIG. 13 shows another optional feature of the reciprocatable extensionmember 240 that is adapted to maintain the proximal end 258 of the jawsin a selected spaced apart position that is substantially parallel.Whereas the upper and lower flange surfaces maintain the engagementsurfaces 355A and 355B with a maximum gap therebetween—the flanges donot create a minimum gap which would occur, for example, if tissue wereengaged at the distal end of the jaw but not at the proximal end of thejaws. Since the pivot is a “floating-type” pivot, the proximal jawportion could be pinched together somewhat if tissue was only engaged bythe distal jaws when the extension member is in its fully extendedposition. FIG. 13 shows the extension member 240 with another cam orengagement surface indicated at 402 (phantom view) that is adapted toslide under and engage the ends 295 of the rectangular pins 274 thuscause the proximal jaw portion 258 to have a minimum gap. Thus, the jawscan be maintained with parallel engagement surfaces even with a“floating” pivot. In another embodiment (not shown), the ends 295 of therectangular pins 274 can be fitted with rollers, bearing or a lubriciouscoating to insure ease of sliding of the extension member against theends 295 of the rectangular pins 274.

Although particular embodiments of the present invention have beendescribed above in detail, it will be understood that this descriptionis merely for purposes of illustration. Specific features of theinvention are shown in some drawings and not in others, and this is forconvenience only and any feature may be combined with another inaccordance with the invention. Further variations will be apparent toone skilled in the art in light of this disclosure and are intended tofall within the scope of the appended claims.

1. A jaw assembly for a medical device, comprising: an instrumentworking end that carries openable-closable paired jaws that define firstand second pivot locations to thereby provide first and secondjaw-closed positions; an elongate jaw defining a first surface portionand a second surface portion for cooperating with moveable cam elements;an axially-moveable extension member carried by the working end, theextension member having a substantially I-beam shape and defining afirst cam element for engaging said first surface portion to rotate thejaw about the first pivot location to move the jaws toward the first jawclosed position wherein the jaw faces are substantially parallel; theextension member defining a second cam element for engaging said secondsurface portion to rotate the jaw about the second pivot location tomove the jaws toward the second jaw closed position wherein the jawfaces are non-parallel with approximated distal jaw tips.
 2. The jawassembly of claim 1, wherein the first pivot comprises a floating-typepivot with at least one projecting element that slidably cooperates withat least one bore in the working end.
 3. The jaw assembly of claim 1,wherein the paired jaws have channel portions therein for slidablyreceiving a transverse portion of the extension member.
 4. The jawassembly of claim 1, wherein the extension member has a first upperflange portion that defines said first cam element.
 5. The jaw assemblyof claim 1, wherein the extension member has a second lower flangeportion that defines said second cam element.
 6. The jaw assembly ofclaim 1, further comprising an electrically conductive material in anengagement surface of at least one jaw for receiving electrosurgicalenergy.
 7. The jaw assembly of claim 1, wherein the extension member hasa distal blade edge for transecting tissue.
 8. The jaw assembly of claim1, wherein the extension member carries a distal cutting electrode fortransecting tissue.
 9. A jaw assembly for a medical device, comprising:an instrument working end extending along an axis with anopenable-closable jaw structure that provides a first paralleljaw-closed position and a second non-parallel jaw-closed position; anextension member that is axially moveable within the working end betweennon-extended and extended positions, the extension member having asubstantially I-beam shape and defining a first cam element for slidablyengaging a first upper surface of a particular jaw and a second camelement for slidably engaging a second lower surface of said particularjaw; wherein movement of the extension member from the non-extendedposition to a first partially extended position causes the jaws to movetoward said first parallel jaw-closed position; and wherein movement ofthe extension member from said first partially-extended position to asecond partially-extended position causes the jaws to move to the secondnon-parallel jaw-closed position with approximated distal jaw tips. 10.The jaw assembly of claim 9, wherein said first and second cam elementsare carried on flange portions of the extension member.
 11. The jawassembly of claim 10, wherein said second lower cam element comprises astep in a said flange portion.
 12. The jaw assembly of claim 10 whereinsaid first cam element is distal to said second cam element relative tothe axis of the extension member.
 13. A jaw assembly for a medicaldevice, comprising: an instrument working end carrying anopenable-closable jaw structure that provides a jaw-open position, afirst jaw-closed position and a second jaw-closed position; an extensionmember that is axially moveable within the working end betweennon-extended and extended positions, the extension member having asubstantially I-beam shape and defining a first cam element for slidablyengaging a first jaw surface and a second cam element for slidablyengaging a second jaw surface; wherein the extension member in apartially extended position engages said first cam element with saidfirst jaw surface to rotate the jaw structure to said first jaw-closedposition; and wherein extension member in an extended position engagessaid second cam element with said second jaw surface to rotate the jawstructure to said second jaw-closed position in which the distal jawtips are approximated.
 14. The jaw assembly of claim 13, wherein saidfirst cam element is a distal surface of the extension member.
 15. Thejaw assembly of claim 13, wherein said second cam element is a surfaceof a flange portion of the extension member.
 16. The jaw assembly ofclaim 13, wherein said second cam element includes a step surface in aflange portion of the extension member.
 17. The jaw assembly of claim13, wherein said first and second jaw surface portions are on respectiveupper and lower portions of a particular jaw.
 18. The jaw assembly ofclaim 13, wherein the jaw structure defines a central channel forslidably receiving a transverse portion of the extension member.
 19. Thejaw assembly of claim 13, wherein the extension member carries opposingfirst and second flange portions that define said first and second camelements, respectively.
 20. The jaw assembly of claim 13, furthercomprising an electrosurgical conductor in an engagement surface of thejaw structure.